All particles exhibit wave-particle duality. And I have a strange question.
Why does a larger system, liken an atom that is just a set of smaller systems, itself exhibit wave-particle duality?
In principle all large systems can be defined as a set of smaller systems. An atom is a set of nucleus (a smaller set of up and down quarks held together by the strong interaction) and some electron(s) bound to the set of quarks by the electromagnetic force.
How is this set of smaller systems being able exhibit wave-particle duality as a whole as if it is a particle itself?
Does this imply that electron and all other elementary particles are indeed just another set of smaller sets and any sets can exhibit wave-particle duality?
And here comes the question: how do you define a set? We naturally define composition such as atom, molecule or "elementary particle" like electron as a set. Can the composition of electrons and up quarks be defined as a set (a system with wavefunction) and the down quarks that present in the atom be defined as a separated set (another system)?